The invention relates to a pressure-stable cylinder/piston unit which blocks water vapor and oxygen and is designed for a needle-free injector, with a chamber arranged in a cylinder, which blocks water vapor and oxygen, and designed for long-term and sterile storage of an injection solution, an end wall with at least one nozzle bore or one outlet element, a pressure-stable outer cylinder, and a pressure-stable piston arranged movably in the chamber and blocking water vapor and oxygen.
The invention further relates to methods for bubble-free, automatic or manual filling of the cylinder/piston unit, also at atmospheric pressure.
Cylinder/piston units are used in injectors and disposable injectors which are known, for example, from US 200810146997 A1 DE 10 2007 004 211 A1 or DE 10 2007 008 369 A1. None of these cylinder/piston units is suitable for long-term storage of injection solutions, e.g. over a year, since they are unable to block water vapor and oxygen.
Injection solution is understood as liquid medicaments. The specialist terms used will now be explained in detail. The term medicament is known to the person skilled in the art. This is understood as substances or mixtures of substances for human or veterinary medicine. They consist of the pharmaceutical active substance or substances, and of further standard components that make this active substance usable pharmaceutically, in particular water.
DE 10 2005 054 600 A1 discloses a cylinder/piston unit having a cylinder and a piston which is guided therein, wherein the cylinder and the piston enclose a chamber that can be filled at least for a time with an active substance, and the cylinder has at least one outlet element at its front end. The cross section of the chamber or the cross section of the cylinder inner wall increases at least in regions from the front to the back. At least in the front area directed toward the outlet element, the piston has a front elastic skirt, the front outer edge of which defines, when the piston is unloaded, a cross-sectional surface which is greater than a surface that is defined by a contour line and that lies in the area of transition from the skirt to the section of the piston carrying the skirt.
DE 10 2006 040 888 B3 discloses a closure system for containers used for storing or administering substances in the form of liquids, pastes or powders, said system consisting of a cap, provided with a through-hole, and of a closure element. The cap holds the closure element with a force fit and/or form fit on the container by means of a catch element present on the container in the area of the opening that is to be closed. The end face which surrounds the opening of the container, and on which the closure element bears, has a depression. The closure element is a virus-proof, bacteria-proof and spore-proof film that lies on the end face and, at least in some areas, over the depression. When the cap is fitted in place, an elastomer ring or adhesive ring is arranged between the closure element and the depression and fills the depression.
DE 10 2006 045 959 B3 discloses a cylinder/piston unit including a cylinder and a piston guided in the cylinder and sealed off in a sterile manner by a rubber seal, wherein the cylinder and the piston enclose a chamber that can be filled at least for a time with active substance, and the cylinder has at least one outlet element at its front end. The piston, resting in a rear position, is sealed off relative to the cylinder in a sterile manner by a static rear sealing element, wherein both sealing elements each respectively bear on the wall of the cylinder and on the wall of the piston in a sealing position. Arranged spatially behind each static sealing element, there is a parking area for receiving the respective sealing element. When the piston is actuated, the individual static sealing elements are transferred from their respective sealing position to a parked position located in the parking area, wherein each sealing element in the parked position touches either only the cylinder wall or only the piston wall. Arranged between the two static sealing elements, there is at least one dynamic sealing element on the piston side, which dynamic sealing element bears on the inner wall of the cylinder at least when the piston is actuated.
In the described cylinder/piston unit, a closure element is inserted as a piston into the prefilled medicament chamber in the vacuum application process. Under vacuum, the closure element is placed on the liquid level of the medicament that has been introduced into the chamber. This method and the devices required for it are expensive and complicated.
Proceeding from this prior art, the objects of the invention are
object 1—to define a pressure-stable cylinder/piston unit which blocks water vapor and oxygen and is designed for long-term sterile storage of an injection solution, and methods for bubble-free filling of the cylinder/piston unit, also in a tray, where the piston can be introduced more easily and at atmospheric pressure into the cylinder, in order to reduce the costs for the device and the method. At the same time, however, it is also intended to allow manual filling, for example of small batch numbers, such that, for example, no filling machine is needed for the clinical specimens;
object 2—to safely avoid underdosing (partial administration) or no dosing (rebound of the injection stream) (no wet-shot);
object 3—to avoid the return flow of injection solution from the injection channel;
object 4—to avoid the bubble formation that is possible starting from administration volumes of more than 150 microliters.